496 is cool but a little pricey for a used engine... 100 some hours for 10,000? I might be confused but I'm pretty sure the brand new 496 is only 12,000 without a drive mounted on it...
If you want a turn key 509 I got a friend selling one out here in CA. He's a Velocity Power boats dealer. 658HP.
Turn key $10,000. Got 5 hours on it and it's in a Scarab with the Hardin Marine Water Jacketed headers for 11,500
Dart block and dart pro 1 heads, Dart intake. Everything is billet or forged. It was done right.